My buddies 07 XKR has had a problem since he bought the car. He will get restricted performance when the engine is above 4000 rpm and above 75% throttle. The codes being thrown very: I got CYL 1,3,5,7 misfire after replacing the spark plugs. I also got a code reporting that it had a misfire in the first 1000 rpm (but the car was running when I reset it, came on shortly after). The car has 102k miles on it. I am thinking O2 sensors, but would expect a direct code relating to the O2 sensors. I can get the exact codes if needed. I was planning on having my friend go to the dealer to have them check it out, but any suggestions on things we could check for little $$ before making the 2 hour journey to the dealer?

 

Please start with the codes.

 

P0301 - Cylinder 1 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0305 - Cylinder 5 Misfire Detected
P0307 - Cylinder 7 Misfire Detected
P0300 - Random/Multiple Cylinder Misfire Detected

 

behaving like bad injector connections. try rechecking them. Next, swap a coil pack out from one misfiring cylinder to a good one and see if your code changes. two free and easy things you can try before the dealership

 

Bad gas or fuel filter are also options to try. fuel injector cleaner, then replace the filter.

 

Thanks, I will give that a try. I was thinking about fuel filter. Where is that on these cars? It does feel like it is hesitating/stumbling when driving normally compared to my XKR so fuel filter or injectors is a great idea.

 

all on the left bank too. I'd say more likely something with the injector wires after changing plugs

 

Sure they were the right plugs? Just wondering.

You could check fuel trims in case there's an air leak (bumped something during the work, gasket twisted, etc).

 

I used the Bosch 9652 Iridium

I think a lack of fuel is likely. Going to do a seafoam treatment and some fuel injector cleaner to see if that fixes it. Looks like removing the fuel injectors involve removing the supercharger? The manual I have wasn't really clear on this one. I'd rather do that and clean them out properly, but not looking forward to removing the supercharger to gain access.

 

Could be a choked catalyst on that bank, similar cases here on the forum in the past.

 

I agree Cambo, just oddly coincidental that the MIL lit up after a spark plug change.

 

The code has been consistant since he baught the car. Plugs were first on the repair list for the listed codes. They didn't solve the problem.

 

Oh my bad. I re-read and now better understand why you went downstream so quickly.

Still fuel filter and injector cleaner are easy first steps. Is the misfiring constant now or still only over 4000 rpm/ 75% throttle?

 

misfiring is consistant when reved over 4000 and pushed some. Clogged cats seem realistic given the symptoms. I'm sure the entire system needs a cleaning.

 

Seafoam cleaned it up, made it run smoother but still same cel when pushed hard. Going to compre fuel pressure readings using my obd2 tool with his car and mine to determine if it is the fuel filter. But first it gets a rubbing compound/polish/wax.

 

Lack of fuel doesn't cause misfires, but choked cats definitely do. I reckon it's the cat/s.

 

Agree, some DIY tests


Put an infrared thermometer on the cat and compare to the right side. Also note the temps at the front should be at least 100 degrees cooler than the rear (rule of thumb). measure temp at the welds, not the shield

If you have one, try placing a vacuum gauge on the intake. google it, it's fairly simple to check.

Second, smack the cat with a rubber mallet. Hear rattling? Cat is bad

3rd, remove an oxygen sensor and install a pressure gauge. again, google it, fairly simple test if you have the gauge.

 

Thanks for the suggestions. I do believe it is the cat now. The question is will california know if I install an out of state cat? The ones online are good priced but I know the jag part is much more. Any suggestions on who to buy from?

 

Please confirm and let us know once you resolve radiatn. It would help others on the forum.

Can't help you with the Cats. You'll need to consult with fellow Californians. No inspections here in MN.

 

One last thing to try before changing the cats.

A bottle of BG 44K, as recommended by Jaguar & Land Rover (see attached bulletin).

SSM46917.pdf

For $30 or whatever a bottle costs, worth a shot before spending a grand on more on cats.

But if the entire bank is misfiring then i'm afraid it does point towards a choked cat. The age/mileage is up there around the same as when my cats on the XJR were choked...